Xylanase treatment of plant cells induces glycosylation and fatty acylation of phytosterols

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Abstract
Treatment of tobacco suspension cells (Nicotiana tabacum cv. KY 14) with a purified β‐1,4‐endoxylanase from Trichoderma viride [1 μg enzyme (ml cells)−1] caused a 13‐fold increase in the levels of acylated sterol glycosides and elicited the synthesis of phytoalexins. A commercial preparation of xylanase from Trichoderma viride caused an identical shift in sterols. In contrast, a commerical xylanase from Aureobasidium pullaulans had no effect on the levels of acylated sterol glycosides, but did elevate the levels of sterol esters. Treatment of the cells with Cu2+ or Ag+ also evoked a severalfold increase in the levels of acylated sterol glycosides. Analysis of the various sterol lipid classes revealed that the large xylanase‐induced increase in acylated sterol glycosides occurred at the expense of sterol esters, free sterols and sterol glycosides. Further analyses revealed that the most abundant phytosterol in each of the four classes of sterol lipids was β‐sitosterol. Linoleic acid was the most abundant fatty acid in the sterol esters, and palmitic and linoleic acids were the most abundant fatty acids in the acylated sterol glycosides. Glucose was the only sugar moiety in the sterol glycoside and acvlated sterol glycosides. Glucose was the only sugar moiety in the sterol glycoside and acylated sterol glycoside fractions. The results of the present study demonstrate that xylanase from Trichoderma viride induces a dramatic shift in the level of acylated sterol glycosides, indicating that endoxylanase was probably the active component in the cellulase enzyme preparations used in our previous study.